In the course of servicing oil and gas wells, it is sometimes necessary to deposit or “dump” materials in a desired downhole location, for example atop a downhole packer. The materials to be dumped may comprise, without limitation, sand, cement, or other generally flowable solids.
The tool used to dump such materials is frequently known in the industry as a “dump bailer.” While dump bailers have been in use for many years, and have taken many forms, one common element is that the dump bailer is a generally elongated tool, for running downhole into a wellbore, and has a cavity within which the material to be dumped is placed. The dump bailer is then run downhole (on a cable or wireline, whether an electric wireline or so-called “slickline”) to the desired location. The cavity is then opened (by various means), and the material flows out of or dumps out of the cavity due to gravity.
Prior art dump bailers have employed various means of opening the cavity to allow the material therein to flow out, depending upon whether the dump bailer is run on electric wireline, which of course permits actuation of a mechanical means by electric current; or a mechanical means. Mechanical means pose a variety of problems, in that it is frequently not possible to verify depth placement of the tool, and actuating the mechanical means at depth is problematic. Dump bailers for use with electric wireline solve some of these issues, but carry their own problems. Prior art dump bailers for use with electric wireline generally employ some sort of explosive charge to create the required opening into the cavity. Due to the explosive charge, it is of critical importance to avoid a premature actuation of the dump bailer. It is well known that stray electric signals, radio signals, etc. pose a risk of actuating the explosive prematurely. It has therefore long been a practice to require all radio communications to be shut down on oil and gas well work sites when such dump bailer is employed. It is readily understood that this shutdown of communications can pose logistical and even safety issues. Related issues with explosive type dump bailers include the need for federal and/or state explosive licenses; Department of Transportation permits; FAA permits; special explosives training for operators, etc.